Bottom Line:
Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed.The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region.In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

ABSTRACTSequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed. Retinal morphology, apoptosis (TUNEL assay), and function (electroretinography; ERG) were examined at several time points after NaIO(3) administration. The higher dose of NaIO(3) caused progressive degeneration of the whole retinal area and total suppression of scotopic and photopic ERG. In contrast, the lower dose induced much less severe degeneration in peripheral part of retina along with a moderate decline of b- and a-wave amplitudes in ERG, corroborating the presence of regions within retina that retain their function. The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region. In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

Fig3: A comparison of outer nuclear layer thickness (μm; mean ± SD) at the different time points after NaIO3 administration at the higher (40 mg/kg) and lower (20 mg/kg) dose. a The central part of the retina (posterior pole), approx. 300 μm from the optic nerve head. b The peripheral part of the retina, approx. 300 μm from the ora serrata. * P < 0.05 lower versus higher dose

Mentions:
The lower concentration of NaIO3 (20 mg/kg) showed much less severe damage to the eye tissues. Damage to the RPE and photoreceptor degeneration were most pronounced in the central region of the retina, with relative sparing of the peripheral retina adjacent to the ora serrata (Fig. 2f, g). Additionally, the lower dose of NaIO3 led to a lessening of RPE and retinal degeneration in the peripheral retina, whereas the histopathological changes within its central region were similar to those observed after the injection of the higher dose of NaIO3. The histological analyses, including measurements of outer nuclear layer thickness both in peripheral and central parts of the retina, are summarized in Fig. 3. Of note, a peak of photoreceptor cell death identified by a TUNEL assay was observed on the 3rd day after NaIO3 administration in both the lower and higher dose models, indicating the time point when the most significant damage within the outer nuclear layer occurred (Fig. 2h, i). What is more, based on the results obtained from the TUNEL method, we found a regional pattern in the form of a more intense apoptotic reaction visible within the central part of the retina than in its peripheral region (Fig. 2a). The morphological changes involving those present in the RPE as well as in photoreceptors are summarized in Table 1.Fig. 3

Fig3: A comparison of outer nuclear layer thickness (μm; mean ± SD) at the different time points after NaIO3 administration at the higher (40 mg/kg) and lower (20 mg/kg) dose. a The central part of the retina (posterior pole), approx. 300 μm from the optic nerve head. b The peripheral part of the retina, approx. 300 μm from the ora serrata. * P < 0.05 lower versus higher dose

Mentions:
The lower concentration of NaIO3 (20 mg/kg) showed much less severe damage to the eye tissues. Damage to the RPE and photoreceptor degeneration were most pronounced in the central region of the retina, with relative sparing of the peripheral retina adjacent to the ora serrata (Fig. 2f, g). Additionally, the lower dose of NaIO3 led to a lessening of RPE and retinal degeneration in the peripheral retina, whereas the histopathological changes within its central region were similar to those observed after the injection of the higher dose of NaIO3. The histological analyses, including measurements of outer nuclear layer thickness both in peripheral and central parts of the retina, are summarized in Fig. 3. Of note, a peak of photoreceptor cell death identified by a TUNEL assay was observed on the 3rd day after NaIO3 administration in both the lower and higher dose models, indicating the time point when the most significant damage within the outer nuclear layer occurred (Fig. 2h, i). What is more, based on the results obtained from the TUNEL method, we found a regional pattern in the form of a more intense apoptotic reaction visible within the central part of the retina than in its peripheral region (Fig. 2a). The morphological changes involving those present in the RPE as well as in photoreceptors are summarized in Table 1.Fig. 3

Bottom Line:
Sequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed.The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region.In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.

ABSTRACTSequential morphological and functional features of retinal damage in mice exposed to different doses (40 vs. 20 mg/kg) of sodium iodate (NaIO(3)) were analyzed. Retinal morphology, apoptosis (TUNEL assay), and function (electroretinography; ERG) were examined at several time points after NaIO(3) administration. The higher dose of NaIO(3) caused progressive degeneration of the whole retinal area and total suppression of scotopic and photopic ERG. In contrast, the lower dose induced much less severe degeneration in peripheral part of retina along with a moderate decline of b- and a-wave amplitudes in ERG, corroborating the presence of regions within retina that retain their function. The peak of photoreceptor apoptosis was found on the 3rd day, but the lower dose induced more intense reaction within the central retina than in its peripheral region. In conclusion, these results indicate that peripheral area of the retina reveals better resistance to NaIO(3) injury than its central part.